Electrolytic capacitors (e.g., tantalum capacitors) are increasingly being used in the design of circuits due to their volumetric efficiency, reliability, and process compatibility. For example, one type of capacitor that has been developed is a solid electrolytic capacitor that includes a tantalum anode, dielectric layer, and conductive polymer solid electrolyte. To help protect the capacitor from the exterior environment and provide it with good mechanical stability, it is typically encapsulated with an epoxy resin. While such epoxy resins are suitable in most environments, they can nevertheless become problematic in certain circumstances. For example, certain types of conductive polymer electrolytes (e.g., PEDT) are highly sensitive due to the tendency of such polymers to readily oxidize in the presence of moisture. Unfortunately, the presence of a very high level of moisture (e.g., 85% relative humidity) in the ambient environment can cause the epoxy resin to slowly weaken or degrade, which may eventually allow a small amount of moisture to penetrate into the interior of the capacitor. This is particularly problematic at high temperatures (e.g., about 85° C.). Even in a small amount, the moisture can result in oxidation of the conductive polymer and lead to a rapid deterioration of the electrical properties.
As such, a need exists for an improved solid electrolytic capacitor for use at high temperature and high levels of humidity.